If a blood test could determine if you'd get Alzheimer's, would you take it?

Early predictors of diseases are on the rise. Do you want to know your risk? (Photo: Getty Images)

Would you want a fortuneteller or time traveler to give you the date and circumstances of your death? That question is still a hypothetical one. But it might not be one day, as medical science has been working hard to find new ways to assess people for risk of specific diseases through diagnostic and genetic testing.

Even though results offer only vague notions of various genetic risks, the spiking popularity of at-home DNA kits has made spitting into a test tube feel a lot like peering into a crystal ball. Doctors, meanwhile, could soon have more reliable predictors in their toolkits. For example, a new report says we’re closing in on the ability to detect Alzheimer’s disease with a simple blood test — up to 20 years before symptoms develop. But with no cure yet available for Alzheimer’s, would you even want to know your risk factor?

“We are getting to this stage of precision medicine in many ways, which is great, but it does raise a number of practical concerns and ethical considerations that have to be worked out,” Keith Fargo, the Alzheimer’s Association’s director of scientific programs and outreach, tells Yahoo Lifestyle.

Bioethicists, psychologists, and patients have been thinking about these concerns for decades, specifically regarding Huntington’s disease, another incurable degenerative brain condition for which extremely accurate genetic testing has been available since 1993. Because Huntington’s is a hereditary disorder, people have often already watched family members succumb to the disease, which usually begins between the ages of 30 and 50. Still, a recent U.K. study reported that more than 80 percent of people at risk for developing it had not been tested.

“People bring their own experiences to receiving information and their desire to have that information,” Marni Amsellem, a New York-based clinical psychologist who works with cancer patients, tells Yahoo Lifestyle.

When testing for Huntington’s first became available, some worried that people who discovered they were carriers were at higher risk for committing suicide (similar to the fears that were debated prior to the more recent FDA approval of an at-home HIV test). In fact, some studies have shown this is not necessarily the case. At the same time, other studies recommend that patients who are already at risk for depression and anxiety not undergo testing.

Everything changes if there’s a chance that you can do something about your test results. The most famous example these days is people who test positive for the BRCA1 or BRCA2 gene mutation, which increases the chance of developing breast and ovarian cancer. Women like Angelina Jolie have opted for prophylactic mastectomies and oophorectomies after receiving their test results. Though it’s still not a complete guarantee against cancer, such surgeries greatly improve one’s odds, Amsellem says. There is also a great value in feeling in control of one’s own health.

“They’re saying, ‘I want to have a future, and this is one way the odds suggest that I will have a healthier future,’” Ansellem says.

There is some limited ability to predict risk for Alzheimer’s disease, according to Fargo, who explains that at-home DNA tests can detect a gene variant called APOe4.

“People who have one copy of APOe4 are about three times as likely to develop Alzheimer’s disease,” Fargo says. “People who have two copies are about eight to 12 times as likely as the general population. That being said, there are lots of people with APOe4 who never develop Alzheimer’s. And lots of people who don’t have even one copy of APOe4 who do develop Alzheimer’s, so that genetic testing doesn’t really do what people might expect that it does, which is tell you whether you’re going to develop the disease.”

Doctors can conduct something called an amyloid positron emission tomography (PET) scan — which involves injecting a tracing substance in the brain to be picked up in an image — on patients to detect the formation of plaques developing in the brain. Those plaques are an early sign of the development of Alzheimer’s disease, though some people never wind up developing dementia, and scientists are still trying to find out why. A blood test, as the one shown to be effective in the recent study, would make this detection much easier. But if no one knows how to prevent the disease, why would it matter to know about it 20 years in advance?

“There are a number of benefits to early and accurate diagnosis,” Fargo explains. “For one thing, probably one of the most important things is that people can participate in a clinical trial. … Many of the clinical trials are prevention trials, which means you’re only eligible for them before you begin to have cognitive decline.”

The Alzheimer’s Association has a trial match tool that allows people to find a clinical trial near them if they’re interested in helping experiment to find new treatments for themselves and others. The association is also conducting a two-year trial to determine whether healthy lifestyle changes can protect the cognitive function in older adults.

The other, less optimistic benefit of early testing is that it gives people time to plan the rest of their lives and what they want their care to look like, and to express their wishes to loved ones before they begin to show signs of decline.

Sometimes these test results aren’t a death sentence, but they’re an opportunity for people to lead the life they really want. Amsellem has seen this in patients after diagnoses and in those who have just made it through a cancer battle.

“A lot of people will end up coming through their cancer experience and say, ‘This job is horrible. My boss is horrible. This isn’t what I want to do. I don’t feel fulfilled,’” she says. “Then they start something new, they quit their job, they approach it very differently.”

Then again, you don’t necessarily have to go through all that to reevaluate your priorities. Long before you’re spurred on by a dire diagnosis, you do have the power to take measures doctors believe will increase your odds of having a longer, higher-quality life. On Alz.org, for instance, you can find a list of “10 Ways to Love Your Brain,” including exercising, sleeping, maintaining friendships, avoiding head injuries, and taking challenging classes — and those seem like pretty good ideas for everyone.

Amsellem understands why many are tempted to find out everything they can about their health with DNA tests and online medical searches.

“It’s kind of a phenomenon of the age that we’re in,” she says. “But it’s something we should be cautious about. I do not think people should make any major decisions without consulting a health care professional.”